GATE 2023 PI – Question 59
An arc weld is made at 25 V, 200 A and speed 2 mm/s. Heat used for melting is 80% of generated heat; unit melting energy is 10 J/mm³. Find volume of weld metal produced per unit time in mm³/s (integer).
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Show answer and explanation
Correct answer: 200 to 200
Explanation
The source and final key disagree dimensionally. Useful melting power is $0.8VI=0.8(25)(200)=4000$ J/s. Dividing by 10 J/mm³ gives the requested physical rate **400 mm³/s**. Dividing this rate by travel speed 2 mm/s instead gives weld cross-sectional area **200 mm²**, the value in the official key. Official grading **200** is preserved, but it corresponds to area, not the printed volume-per-time quantity.